Soil Biophilic Elements (C, N, P) and Microbial Activity in Forest Parks of Moscow and Suburban Forests

In six forest parks of Moscow and four suburban forests (5 plots each, n = 50), soil physical, chemical, and microbial properties of the upper 10-cm layer were assessed in combination with vegetation properties. The contents of carbon (C), nitrogen (N), and phosphorus (P) in soil and microbial biomass were determined. It was revealed that soil bulk density; pH value; and contents of N-NO3-,Ca, and heavy metals (Pb, Cu, Ni, Zn) increase in forest parks of Moscow in comparison with those in suburban forests. In the soils of forest parks, a decrease in the microbial biomass C (C-mic) content, basal respiration (BR), and microbial C and N availability (C-mic/C, N-mic/N, BR/C) took place. The changes in soil microbial properties were mainly driven by the decrease in abundance of leaf litter and the available soil C content (13-35% of the explained variance). The microbial response of soil microorganisms to input of low molecular weight organic substrates (carbohydrates, carboxylic and phenolic acids, amino acids, amino sugars) in forest parks and suburban forests did not differ significantly. In the soils of forest parks, no changes in microbial mineralization and immobilization of P (P-mic, P-mic/P) were found. The impact of urbanization on the forest ecosystems led mainly to a decrease in the intensity of soil C and N cycles. Apparently, these changes were caused by the recreational activity and management practices applied to green spaces in the city, which led, in particular, to a decrease in the amount of forest litter in urban parks compared to suburban forests.